The present invention relates broadly to a flexible reinforced hose construction of a push-on variety for use in conjunction with a fitting end configured as an insertable, barbed nipple, and more particularly to such a hose construction having a polyurethane or other thermoplastic inner core tube element which exhibits a reduced coefficient of friction.
Flexible “push-on” tubing and hose, which for purposes of convenience is referred to herein simply as “hose,” is used in a variety of fluid transfer applications for conveying fluid pressures which typically are in the range of from about 60 psi (0.5 MPa) to 500 psi (3.5 MPa) or more. Representative applications include use as shop air lines, and as industrial or automotive water, gasoline, oil, and antifreeze lines. By “push-on,” it is meant that one or both of the terminal ends of the hose may be frictionally sleeved over an associated fitting or other connector adapted as having a distal or free end configured as a barbed nipple. That is, the nipple end of the fitting is insertable into the hose which is “self-gripping” such that the inner diameter of the hose is resiliently expanded and recovered to develop radially compressive forces retaining the nipple within the hose in a fluid-tight engagement. Advantageously, the described hose and fitting arrangement may be used to without auxiliary ferrules, wires, shells, crimps, or clamps, and thereby provides for a rapid, easily replaceable assembly at a relatively low cost.
In basic structure, hoses of the “push-on” type herein involved typically are constructed as having a tubular, innermost core surrounded by one or more outer layers of a fiber reinforcement. The reinforcement, in turn, is protected by a surrounding outermost sheath or cover which may be of the same or different material as the core tube. The cover also provides the hose with increased abrasion resistance.
The core tube, which may be a thermoplastic material such as a polyamide, polyolefin, polyvinyl chloride, or polyurethane, or a synthetic rubber material such as Buna N or neoprene, may be conventionally extruded and cooled or cured. As is detailed in U.S. Pat. Nos. 3,116,760; 3,159,183; 3,966,238; 4,952,262, the tube may be cross-headed extruded on a mandrel for support, or otherwise supported in later forming operations using air pressure and/or reduced processing temperatures. From the extruder, the tube may be collected on a reel or other take-up device for further processing. As dispensed from the reel or, in a continuous in-line process, taken directly from the extruder, the tube, which may be frozen or otherwise chilled, such as by being sprayed with a liquid and gaseous nitrogen mixture or the like to improve dimensional stability, next may be passed through an applicator for its coating with an outer layer of an adhesive material which may be a polyurethane or other isocyanate-based adhesive. The adhesive-coated core tube then may be delivered through one or more braiders or winders which may be used to surround the tube with one or more reinforcement layers of a fibrous material such as a monofilament, yarn, or wire. The reinforcement layers, which may be applied under tension and bonded to the core tube via the adhesive layer, typically may be formed of an interwoven braid or a spiral winding of a nylon, polyester, or aramid yarn, or a metal wire.
Following the application of the reinforcement layer, a second adhesive layer may be applied to bond the reinforcement to the outer cover or sheath. Such cover, which may be applied as a cross-head extrusion or a spiral-wound wrapping, typically is formed of abrasion-resistance polymeric material such as a polyamide, polyolefin, polyvinyl chloride, or polyurethane. Again, the adhesive layer bonds the outer cover to the reinforcement layer.
A representative push-on hose construction is described in commonly assigned U.S. Pat. No. 3,966,238. Such constriction involves a core tube formed of a synthetic rubber or plasticized polyvinyl chloride, a braided non-metallic fibrous reinforcement, and an outer cover of a synthetic rubber or plasticized polyvinyl chloride. Another representative push-on hose construction is described in U.S. Pat. No. 3,210,100 as adapted for use with a tubular hose nipple having a plurality of annular barbs. Hoses of these types are manufactured and sold commercially by Parker-Hannifin Corp. of Cleveland, Ohio, under the trademark PUSH-LOK®.
Other composite hose constructions and methods for constructing the same are described in commonly-assigned U.S. Pat. Nos. 4,952,262; 4,699,178; 4,384,595; and 4,273,160, in U.S. Pat. Nos. 3,711,130; 3,332,447; 3,266,527; 3,251,381; 3,159,183; 3,116,760; 2,805,088, and in British patent No. 737,216. Barbed hose nipples, connectors, and couplings are described in U.S. Pat. Nos. 3,154,329 and 1,996,855; in British Patent Nos. 878,599 and 438,250, and in German Auslegeschrift No. 1,223,209.
Other push-on type hoses and fittings therefor are described in U.S. Pat. Nos. 3,711,130 and 2,805,088, with other flexible reinforced hose constructions being shown in commonly-assigned U.S. Pat. Nos. 4,952,262; 4,699,178; 4,384,595; and 4,273,160, in U.S. Pat. Nos. 3,332,447; 3,266,527; 3,251,381; 3,159,183; 3,116,760; and 2,854,030, and in British Patent No. 737,216. Barbed hose nipple fittings are described in U.S. Pat. Nos. 3,759,445; 3,154,329; and 1,996,855, in British Patent Nos. 878,599 and 438,250, and in German Auslegeschrift No. 1,223,209.
In view of the foregoing, it will be appreciated that the core tube of a push-on hose construction must exhibit a demanding balance of mechanical and other physical properties for the proper performance of the ultimate fitting assembly. Indeed, the hose must be able to be pushed onto the fitting over the barbs of the nipple end without excessive force as this operation often is performed manually. Once assembled, however, the joint must be able to withstand repeated cycles of pressure pulses, without leakage or the blowoff of the hose from the fitting, at service temperature extremes of −40° F. (−40° C.) to 200° F. (93° C.). Accordingly, core tubes heretofore have been constructed of a synthetic rubber material, such as Buna N or neoprene, or from a thermoplastic elastomeric material such as polyvinyl chloride having a relatively high coefficient of friction.
However, as commercial applications for push-on hoses have increased, there have been calls from industry further improvements in such hoses and in the materials of construction therefor. Especially desired would be a construction which facilities hand assembly by reducing the force typically required to insert the fitting into the hose, but which also is able to withstand repeated pressure cyclings without leakage or blowoff.